1. Field of the Invention
This invention relates to magnetic alloy thin films which are particularly suitable for use as a material for magnetic transducer heads for VTR adapted to use in association with magnetic recording media having high coercive force, such as metal magnetic tapes, and which have high saturation magnetic flux density and high permeability.
2. Description of the Prior Art
Among known ternary alloys of Fe--Al--Si, an alloy having a composition of Si.perspectiveto.9.5 wt % and Al.perspectiveto.5.4 wt % is called Sendust alloy. This alloy has a magnetostriction constant and crystalline magnetic anisotropy constant of each approximately zero, with very good soft magnetic properties. Although the Sendust alloy has poor workability and is difficult in making thin pieces by machining, it is easy to obtain a thin film from the alloy by utilizing thin film formation techniques such as sputtering. In addition, the alloy has good resistances to corrosion and wear, so that it may be utilized as a core material for magnetic transducer head, which is used in a high frequency range such as in VTR. On the other hand, one of measures of improving a recording density in magnetic recording art includes use of a shorter wave for recording. However, in order to suppress the self-demagnetizing effect while permitting recording and reproduction of high quality, it is necessary to increase the coercive force of a recording medium. To this end, magnetic recording media having high coercive force, e.g. metal magnetic tapes, have appeared. In order to permit complete recording and erasure while making the best use of the characteristics of the magnetic recording media having high coercive force, materials for magnetic transducer heads should have high saturation magnetic flux density in correspondence to the high saturation magnetic flux density of the magnetic media. If recording and reproducing operations are effected on the same head, permeability as well as the saturation magnetic flux density should be high.
At present, attention is directed to the Sendust alloy since the alloy is considered to be a material which almost satisfy the above requirements. However, the saturation magnetic flux density of the Sendust alloy is about 11000 G and cannot be a material which makes the best use of the characteristics of a metal magnetic tape having a coercive force (Hc) of about 1400 Oe. Thus, there is a high demand for materials which have a saturation magnetic flux density higher than the Sendust alloy and have a permeability equal to or larger than the Sendust alloy.
It will be noted that if it is sufficient to increase only the saturation magnetic flux density, this may be achieved, to an extent, by reducing the contents of Si and Al in the Sendust alloy composition. However, when the Sendust alloy is so formulated as to deviate from a so-called standard composition, it becomes difficult to make the magnetostriction and magnetic anisotropy zero at the same time. This will impede soft magnetic properties inherent to the Sendust alloy.